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WWUS20 KWNS 132100

SEL9

SPC WW 132100

IDZ000-MTZ000-ORZ000-WAZ000-140400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 159

NWS STORM PREDICTION CENTER NORMAN OK

300 PM MDT MON MAY 13 2013



THE NWS STORM PREDICTION CENTER HAS ISSUED A



* SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

  CENTRAL IDAHO

  WESTERN MONTANA

  EXTREME NORTHEAST OREGON

  EXTREME SOUTHEAST WASHINGTON



* EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 300 PM UNTIL

  1000 PM MDT.



* PRIMARY THREATS INCLUDE...

  SEVERAL DAMAGING WIND GUSTS TO 70 MPH POSSIBLE

  SEVERAL LARGE HAIL EVENTS TO 1.5 INCHES IN DIAMETER POSSIBLE



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 60

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES NORTH

NORTHWEST OF BAKER OREGON TO 55 MILES EAST NORTHEAST OF GREAT

FALLS MONTANA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



PRECAUTIONARY/PREPAREDNESS ACTIONS...



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



&&



DISCUSSION...THUNDERSTORMS ARE DEVELOPING OVER NERN OREGON AND

ADJACENT PARTS OF CENTRAL ID IN ADVANCE OF A STRONG SHORT WAVE

TROUGH MOVING EWD INTO WA/OREGON.  SUFFICIENT MOISTURE WITH SURFACE

DEW POINTS IN THE 40S AND A DEEP MIXED LAYER AND STEEP LAPSE RATES

WILL ENHANCE POTENTIAL FOR DAMAGING WIND GUSTS AND HAIL WITH

STRONGER HIGH-BASED STORMS.  THE ACTIVITY IS EXPECTED TO SPREAD

RAPIDLY ENEWD THROUGH THE EVENING HOURS OVER PARTS OF WRN MT.

ADDITIONAL STORMS MAY ALSO FORM EWD OVER THE CENTRAL MT MOUNTAINS

WITHIN THE NEXT SEVERAL HOURS...AND MODEL GUIDANCE SUGGESTS AN

ADDITIONAL WATCH FARTHER EAST IN MT MAY BE NEEDED DURING THE LATE

AFTERNOON OR EVENING.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 400. MEAN STORM

MOTION VECTOR 24040.





...WEISS

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